34 Tex. Admin. Code § 123.8
Except as otherwise expressly provided below, (i) if a member or retiree designates a person who is his or her spouse as a beneficiary and becomes divorced from that person, then the beneficiary designation automatically becomes void as to that person upon divorce, and (ii) to have such person become a beneficiary again, the person must be designated as a beneficiary on the system's appropriate beneficiary designation form completed and filed with the system after the date of divorce. In the event a retiree names a person who is his or her spouse as beneficiary on an optional service retirement annuity selected pursuant to §§854.104(c)(1), (2) or (5) of the Act, and becomes divorced from such person after the retiree's effective date of retirement, the divorce does not automatically void such beneficiary designation.
34 Tex. Admin. Code § 123.8